Category: Vector Biology Objective Questions

Vector Biology Multiple Choice Questions on “Vectors and Cloning in Gram – Positive Bacteria – 1”.

1. In Gram-positive bacteria, there is a disparity in ___________ in the genomes.
A. AT content
B. GC content
A. Structure
D. Composition
Answer: B
Clarification: In Gram-positive bacteria, the base composition of the different genomes ranges from less than 30 percent to more than 70 percent.

2. There are no universal cloning vectors for use with all Gram-positive bacteria.
A. True
B. False
Answer: A
Clarification: Given the disparity in GC content, the base composition of the different genomes ranges from less than 30 percent to more than 70 percent.

3. Streptomycetes are ______________
A. High GC content
B. Low GC content
A. Gram-negative bacteria
D. Low AT content
Answer: A
Clarification: There are no universal cloning vehicles for use with all Gram-positive bacteria. One set of systems has been developed for high-GC organisms such as Streptomycetes and another for low-GC organisms.

4. Which of the following is not a lactic acid producing bacteria?
A. Streptococcus
B. Lactococcus
A. Lactobacillus
D. Clostridium
Answer: D
Clarification: The latter group comprises bacteria from unrelated genera Bacillus, Clostridium and lactic acid producing bacteria lactococcus, streptococcus, lactobacillus.

5. Bacillus subtilis is a _________ bacteria.
A. Gram-negative
B. Low-GC
A. High-GC
D. High-AT
Answer: B
Clarification: Many of the cloning vectors used with Bacillus Subtilis and other low-GC bacteria are derived from plasmids found in Staphylococcus aureus.

6. Cloning vectors for low-GC bacteria are derived from ________
A. Plasmids
B. Yeasts
A. Plants
D. Mammals
Answer: A
Clarification: Many of the cloning vectors used with Bacillus Subtilis and other low-GC bacteria are derived from plasmids found in Staphylococcus aureus.

7. Plasmids from S. aureus transform into B. subtilis and express _____________ normally.
A. Lactic acid
B. Antibiotic resistance
A. Antibiotics
D. Crown gall
Answer: B
Clarification: Plasmids from S.aureus can be transformed into B.subtilis, where they replicate and express antibiotic resistance normally.

8. S. aureus plasmids carry ______ selectable markers.
A. More than one
B. One
A. No
D. Two
Answer: B
Clarification: None of the S. aureus plasmids carries more than one selectable marker and so improved vectors have been constructed by gene manipulation.

9. Vector PC194 carries ____ gene of PT127.
A. TCR
B. PCR
A. CCR
D. GCR
Answer: A
Clarification: Improved vectors have been constructed by gene manipulation.
For example, pHV11 is PC194 carrying the TCR gene of pT127.

10. Which of the following is greatly reduced in plasmid vectors post insertion of exogenous DNA?
A. Size
B. Stability
A. Infection
D. Efficiency
Answer: B
Clarification: In general, plasmids are stable in Bacillus subtilis, but segregative stability is greatly reduced following insertion of exogenous DNA.

11. Which of the following is a cryptic Bacillus plasmid?
A. Pta1060
B. Pta1100
A. Pta 10
D. BSA
Answer: A
Clarification: Stable host-vector systems in B.subtilis are more likely if endogenous plasmids are used. Bron and colleagues have developed the cryptic Bacillus plasmid.

12. Hybrid vectors can replicate both in ________ and B. subtilis.
A. Mammals
B. Insects
A. Plants
D. E.coli
Answer: D
Clarification: Because of difficulties experienced in direct cloning in B.subtilis, hybrid plasmids were constructed which can replicate in both E.coli and B. subtilis.

13. Which of the following is not a filamentous coliphage vector?
A. M13
B. Lambda
A. F1
D. Fd
Answer: B
Clarification: M13, F1, FD are filamentous coliphages containing a circular single-stranded DNA molecule. These have been developed as vectors because of various advantages.

14. Coliphages are single-stranded vectors.
A. True
B. False
Answer: A
Clarification: M13, F1, FD are filamentous coliphages containing a circular single-stranded DNA molecule. These have been developed as vectors because of various advantages.

15. What is the average size of single-stranded vector?
A. 6400 nucleotides
B. 1200 nucleotides
A. 2500 nucleotides
D. 5500 nucleotides
Answer: A
Clarification: The phage particles have dimensions 900*9 nm and contain a single-stranded circular DNA molecule, which is 6407 (M13) or 6408 (fD).

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Vector Biology Multiple Choice Questions on “Vectors for Mammals – 4”.

1. How many routes are available for the biosynthesis of nucleotides in human beings?
A. 1
B. 2
A. 3
D. 4
Answer: B
Clarification: In mammals, nucleotides are produced via two alternate routes, the de novo and the salvage pathway.

2. What are the basic precursors in the de novo pathway of nucleotide synthesis?
A. Carbohydrate, proteins
B. Sugars, amino acids
A. Sugars, vitamins
D. Minerals, carbohydrates
Answer: B
Clarification: In mammals, nucleotides are produced via two alternate routes, the de novo and the salvage pathway. In the de novo pathway, nucleotides are synthesized from basic precursors such as sugars and amino acids.

3. In the salvage pathway, nucleotides are synthesized by the recycling of ___________
A. DNA
B. RNA
A. DNA, RNA
D. Sugars
Answer: C
Clarification: In mammals, nucleotides are produced via two alternate routes, the de novo and the salvage pathway. Salvage pathway recycles nucleotides from DNA and RNA.

4. De novo pathway is exploited for the selection of cells carrying functional HPRT and TK genes.
A. True
B. False
Answer: B
Clarification: If the de novo pathway is blocked, nucleotide synthesis becomes dependent on the salvage pathway, and this can be exploited for the selection of cells carrying functional HPRT and TK genes.

5. The drug aminopterin blocks the _________ of two enzymes.
A. Salvage pathway
B. De novo synthesis
A. Expression
D. Recombination
Answer: B
Clarification: The drug aminopterin blocks the de novo synthesis of inosine monophosphate (IMP) and thymidine monophosphate (TMP).

6. What do you understand by the term “co-transformation”?
A. Integration of 2 transgenes
B. Integration of similar transgenes
A. Integration of a group of transgenes
D. Integration of chromosomal DNA
Answer: A
Clarification: The transfection with two physically unlinked DNAs results in co-transformation that is the integration of both the transgenes into the genome.

7. Southern blot hybridization is done for testing the presence of _________ in a selection of transformants.
A. Non-selected DNA
B. Selected plasmid DNA
A. Genomic DNA
D. Selected genomic DNA
Answer: A
Clarification: To obtain co-transformants, cells were transfected with HSV Tk gene and well defined plasmid DNA. Cells selected on HAT medium are then tested by southern blotting for the presence of non-selected DNA.

8. What is the prerequisite for co-transformation phenomenon to occur?
A. Selectable marker
B. HSV
A. Thymidine kinase
D. PBR322 DNA
Answer: A
Clarification: The phenomenon of co-transformation allows the stable introduction of any foreign DNA sequence into mammalian cells as long as a selectable marker is introduced at the same time.

9. HSV TK gene is a type of __________ marker.
A. Exogenous
B. Endogenous
A. Recombinant
D. Hybrid
Answer: B
Clarification: The HSV Tk gene is a representative of a class of genes known as endogenous markers because they confer a property that is already present in the wild-type cells.

10. The endogenous selectable markers can be used only with mutant cell lines.
A. True
B. False
Answer: A
Clarification: The major disadvantage of the endogenous selectable markers is that they can only be used with mutant cell lines in which the corresponding host gene is non-functional.

11. Dominant selectable markers can be used with __________
A. Any cell type
B. Mutant cells
A. Wild-type cells
D. Recombinant cells
Answer: A
Clarification: Endogenous markers are largely superseded by so-called dominant selectable markers, which confer a phenotype that is entirely novel to the cell and can hence be used in any cell type.

12. What are the dominant selectable markers?
A. Drug-resistance genes
B. Inducing genes
A. Exogenous genes
D. Endogenous genes
Answer: A
Clarification: The dominant selectable markers are usually drug-resistance genes of bacterial origin and transformed cell is selected on a medium that contains the drug at an appropriate concentration.

13. Methotrexate is an analog of __________
A. Aminopterin
B. Kanamycin
A. Folic acid
D. Gentamycin
Answer: C
Clarification: Methotrexate is a folic acid analog, which is a competitive inhibitor of the enzyme dihydrofolate reductase (DHFR).

14. With respect to mammalian cell cloning, salmon sperm DNA can serve as a source of ____________
A. Non-specific carrier
B. Specific carrier
A. Genomic DNA
D. Plasmid DNA
Answer: A
Clarification: Calcium phosphate transfection is mostly used and the specific donor DNA is often bulked with a non-specific carrier such as cleaved Salmon sperm.

15. One application in which the use of plasmid vectors is critical, in the case of mammals is ____________
A. Stable transformation
B. Transient transformation
A. Transfection
D. Transduction
Answer: B
Clarification: One application in which the use of plasmid vectors is critical, in the case of mammals is a transient transformation. Here the goal is to exploit the short term persistence of extrachromosomal DNA.

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Vector Biology Interview Questions and Answers focuses on “Cloning Vectors for E.Coli – 2”.

1. What is an additional feature of M13mp7?
A. 2 antibiotic resistance genes
B. Bigger size
A. Multiple cloning sites
D. Smaller size
Answer: C
Clarification: The M13mp7 contains multiple cloning sites all clustered into the polylinker and this polylinker is artificially synthesized and then inserted in the intergenic sequence.

2. What is a phagemid?
A. A hybrid vector
B. Phage vector
A. Plasmid vector
D. Viral vector
Answer: A
Clarification: Phagemid is a hybrid of M13 phage and Pbr322 plasmid. Pembl8 is an example of phagemid which was created by transferring into a pUC8 a 1300 bp fragment of M13 genome.

3. What does the M13 fragment in a phagemid contain?
A. BamHI restriction site
B. Signal sequences
A. Origin of replication
D. Promoter sequence
Answer: B
Clarification: These signal sequences are recognized by the enzymes that convert the normal double-stranded M13 molecule into single-stranded DNA before secretion of new phage particles.

4. Why is a helper phage needed when cloning experiments which a hybrid vector such as Pembl8 is done?
A. Efficient insertion
B. Attachment to host
A. To provide replicative enzymes
D. Stable transformation
Answer: C
Clarification: The hosts for Pembl8 cloning experiments are subsequently infected with a normal M13 to act as a helper phage, providing necessary replicative enzymes and phage coat proteins.

5. How can the recombinants of phagemid vector Pembl8 be identified?
A. Agar plating
B. Agar + Antibiotic
A. Agar + X-gal
D. Minimal media plating
Answer: C
Clarification: Pembl8, being derived from Puc8, has the polylinker cloning sites within the lacZ’ gene. So recombinants can be identified by the lac selection system.

6. What is the size of fragments that can be obtained by using a phagemid vector?
A. 1 kb
B. 10 kb
A. 1500 bp
D. 50 kb
Answer: B
Clarification: With a phagemid vector such as Pembl8, single-stranded versions of cloned DNA fragments up to 10 kb can be obtained, greatly extending the range of M13 cloning system.

7. What is the size limit for in vitro packaging of an unmodified lambda vector?
A. 10 kb
B. 52 kb
A. 100 kb
D. 10 bp
Answer: B
Clarification: The lambda DNA molecule can be increased in size by only 5%, representing the addition of only 3 kb of new DNA. If total size of the molecule id more than 52 kb, then it cannot be packaged.

8. Which non-essential region of the lambda phage can be deleted without impairing viability?
A. Protein coding
B. Promoter region
A. Integration and excision region
D. Terminator region
Answer: C
Clarification: The removal of non- essential region between 2 to 35 positions on the restriction map decreases the size of the vector by 15 kb and increasing its efficiency of carrying foreign DNA.

9. What is the basic difference between a modified (non-essential regions removeD. and an unmodified lambda vector?
A. Gene expression increases
B. Stable infection
A. Non- lysogenic cycle
D. Star activity
Answer: C
Clarification: Since the non-essential region of the lambda genome which is responsible for integration into the host genome is removed, it no longer follows the lysogenic cycle hence goes infecting the cell and eventually losing them.

10. Why is natural selection used to isolate modified lambda that lacks certain restriction sites?
A. Strains that lack sites are known
B. Easier than in vitro mutagenesis
A. There are no restriction sites in lambda
D. Natural selection is less time consuming
Answer: A
Clarification: There are multiple recognition sites in a lambda phage and only mutant strains that contain not many of these sites can be used as cloning vectors. To get hold of such mutant strains a host E.Coli strain that produces EcoR1 is used.

11. Why is natural selection used to isolate modified lambda that lacks certain restriction sites?
A. Strains that lack sites are known
B. Easier than in vitro mutagenesis
A. There are no restriction sites in lambda
D. Natural selection is less time consuming
Answer: A
Clarification: There are multiple recognition sites in a lambda phage and only mutant strains that contain not many of these sites can be used as cloning vectors. To get hold of such mutant strains a host E.Coli strain that produces EcoR1 is used.

12. Insertion and replacement vectors are modified vectors of which of the following?
A. Plasmid
B. Lambda phage
A. M13 phage
D. Yeast artificial chromosome
Answer: B
Clarification: Once the problems associated with lambda vector; packaging constraints and multiple restriction sites had been solved, development of different types of modified lambda vectors is done.

13. What type of vector is the lambda-gt10?
A. Insertion vector
B. Replacement vector
A. Hybrid vector
D. Unmodified lambda vector
Answer: A
Clarification: It is a vector which can carry up to 8 kb of new DNA, inserted into unique EcoR1 site located in the Ci gene. Recombinants are distinguished as clear plaques.

14. Which property is not associated with a lambda insertion vector?
A. Non-essential region removed
B. Two vector arms ligated together
A. At least one restriction site is present
D. Expression of the gene can be obtained
Answer: D
Clarification: Insertional lambda vectors are cloning vectors and not expression vectors because they do not contain promoter sequences and ribosomal binding sites and hence the expression of the inserted gene cannot be obtained.

15. How can identification of recombinants of lambda-gt10 vector be done?
A. Ampicillin resistance
B. Lac selection
A. cI gene insertional inactivation
D. Agar and X-gal plating
Answer: C
Clarification: The foreign DNA in this vector is cloned within the cI gene containing the EcoR1 restriction site. The recombinants hence are distinguished as clear plaques from the non-recombinant turbid plaques.

To practice all areas of Vector Biology for Interviews, .

Gene Manipulation Multiple Choice Questions on “Applications of Gene Manipulation”.

1. How many routes are available for the biosynthesis of nucleotides in human beings?
A. 1
B. 2
A. 3
D. 4
Answer: B
Clarification: In mammals, nucleotides are produced via two alternate routes, the de novo and the salvage pathway.

2. What are the basic precursors in the de novo pathway of nucleotide synthesis?
A. Carbohydrate, proteins
B. Sugars, amino acids
A. Sugars, vitamins
D. Minerals, carbohydrates
Answer: B
Clarification: In mammals, nucleotides are produced via two alternate routes, the de novo and the salvage pathway. In the de novo pathway, nucleotides are synthesized from basic precursors such as sugars and amino acids.

3. In the salvage pathway, nucleotides are synthesized by the recycling of __________
A. DNA
B. RNA
A. DNA, RNA
D. Sugars
Answer: C
Clarification: In mammals, nucleotides are produced via two alternate routes, the de novo and the salvage pathway. Salvage pathway recycles nucleotides from DNA and RNA.

4. De novo pathway is exploited for the selection of cells carrying functional HPRT and TK genes.
A. True
B. False
Answer: B
Clarification: If the de novo pathway is blocked, nucleotide synthesis becomes dependent on the salvage pathway, and this can be can be exploited for the selection of cells carrying functional HPRT and TK genes.

5. The drug aminopterin blocks the _________ of two enzymes.
A. Salvage pathway
B. De novo synthesis
A. Expression
D. Recombination
Answer: B
Clarification: The drug aminopterin blocks the de novo synthesis of inosine monophosphate (IMP) and thymidine monophosphate (TMP).

6. What do you understand by the term “co-transformation”?
A. Integration of 2 transgenes
B. Integration of similar transgenes
A. Integration of a group of transgenes
D. Integration of chromosomal DNA
Answer: A
Clarification: The transfection with two physically unlinked DNAs results in co-transformation that is the integration of both the transgenes into the genome.

7. Southern blot hybridization is done for testing the presence of _________ in the selection of transformants.
A. Non-selected DNA
B. Selected plasmid DNA
A. Genomic DNA
D. Selected genomic DNA
Answer: A
Clarification: To obtain co-transformants, cells were transfected with HSV Tk gene and well-defined plasmid DNA. Cells selected on HAT medium are then tested by southern blotting for the presence of non-selected DNA.

8. Incorporation of ribozymes into antisense RNA leads to their __________
A. Activity
B. Temperature change
A. Cleavage
D. Regeneration
Answer: C
Clarification: The incorporation of ribozyme catalytic centers into antisense RNA allows the ribozyme to be particularly targeted and then cleaved and degraded.

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Gene Manipulation Multiple Choice Questions on “Gene Sequencing”.

1. Chain-termination is a type of ______________
A. Sequencing
B. Vector generation
A. Antibiotic production
D. Gene manipulation
Answer: A
Clarification: One of the commonest methods of sequencing is the Sanger sequencing which is also known as chain-termination.

2. The first significant DNA sequence to be obtained was that of ________
A. Lambda
B. Plasmid
A. Lactose
D. Mammals
Answer: A
Clarification: The first significant DNA to be obtained was that of cohesive ends of lambda which were 12 bases long; in the year 1971.

3. Plus and minus sequencing is the other name for Sanger sequencing.
A. True
B. False
Answer: A
Clarification: Plus and minus sequencing was used by Sanger in 1977 to sequence the 5386 base pairs long PhiX174 genome. This method was later superseded by Maxam Gilbert method.

4. Which type of DNA cleavage is done in the Maxam Gilbert method?
A. Edge
B. Interstitial
A. Base-specific
D. Gene-specific
Answer: C
Clarification: The Maxam Gilbert method of sequencing was devised in 1977. It uses a variety of chemical reagents to bring about base-specific cleavage of DNA.

5. Sequence of which of the following cannot be determined using the Maxam Gilbert method?
A. Bacteria
B. Plants
A. Bacteriophage T7
D. Plasmid
Answer: C
Clarification: Although Maxam Gilbert is a popular technique of gene sequencing and it superseded the Sanger sequencing method; it has not been used to sequence the genome of T7 phage.

6. What is the main enzyme component of Sanger sequencing?
A. Helicase
B. Polymerase
A. Nuclease
D. Gyrase
Answer: B
Clarification: The chain-termination or dideoxy method of DNA sequencing capitalizes on two unique properties of DNA polymerase enzyme.

7. Which of the following is used by DNA polymerase as a substrate?
A. Sucrose
B. Lactose
A. Nucleotide
D. Nucleoside
Answer: C
Clarification: The DNA polymerase enzymes used in the chain-termination method of sequencing can synthesize a complimentary copy of single-stranded DNA and can use nucleotides as substrates.

8. Which of the following act as chain terminator?
A. Exogenous
B. DNA
A. Deoxynucleotides
D. Dideoxynucleotides
Answer: D
Clarification: A complementary strand is synthesized by the DNA polymerase and whenever an analog which is basically a dideoxynucleotide is incorporated in the growing chain, the chain is terminated.

9. The Klenow fragment is basically a _______________
A. DNA hybrid
B. DNA polymerase
A. RNA polymerase
D. Promoter
Answer: B
Clarification: Klenow fragment is a DNA polymerase which is used in the Sanger sequencing method. It lacks the exonuclease activity, associated with intact enzyme.

10. ____________ is a chemically synthesized oligonucleotide.
A. Klenow fragment
B. DNA
A. Primer
D. RNA
Answer: C
Clarification: Initiation of DNA synthesis requires a primer and usually this is a chemically synthesized oligonucleotide which is annealed close to the sequence being analyzed.

11. How many types of deoxynucleoside triphosphates are used in Sanger sequencing?
A. 1
B. 2
A. 3
D. 4
Answer: D
Clarification: Four different types of deoxynucleoside triphosphates are used, one or more of which is labeled with phosphorus-32.

12. Prior to getting electrophoresed in the sequencing gel, DNA is ____________
A. Purified
B. Denatured
A. Synthesized
D. Fragmented
Answer: B
Clarification: After a suitable incubation period for the DNA mix that contains deoxynucleoside triphosphates, dideoxynucleotides and sample DNA, the DNA is denatured before electrophoresis.

13. A sequencing gel is a ________________ gel.
A. Toxic
B. Highly-polymerized
A. High resolution
D. Low resolution
Answer: C
Clarification: The sequencing gel is a high resolution gel designed to fractionate single-stranded DNA fragments on the basis of their size.

14. What is the molarity of urea used in sequencing gels?
A. 1 M
B. 3 M
A. 5 M
D. 7 M
Answer: D
Clarification: The high-resolution sequencing gels can resolve fragments differing by just one base. These contain 6-20% acrylamide and 7 M urea.

15. The function of urea in the sequencing gels is to promote adherence.
A. True
B. False
Answer: B
Clarification: The sequencing gels contain 6-20% acrylamide and 7 M urea. The function of urea is to minimize DNA secondary structure which affects electrophoretic mobility.

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